In the last 15 years, the use of horizontal underground drilling has become increasingly effective, and more widely accepted for the installation of water and gas pipes, underground utilities, telephone lines, and cables. Prior to the use of these horizontal drilling techniques, open trenches were required to primarily place pipes, cables and wires underground. Particular difficulties were encountered in crossing bodies of water, roads, driveways, improved areas, or existing sewer and water installations. Accordingly, directional horizontal drilling techniques have allowed for the elimination of open trenches, particularly when encountering obstacles at or near the surface.
With the development of these horizontal drilling techniques, there has been an historic need to develop a more precise and cost effective system to effectively control the route of travel, depth of travel and point of emergence for the drilling apparatus. In response to these needs, the radio transmitting unit was developed and incorporated into the drilling apparatus to broadcast a remote signal which would aid in identifying the position, direction of travel and pitch of the drilling apparatus. Improvements have been noted in some areas of underground directional drilling, but the ability to efficiently and cost effectively control the direction of the drilling head when in rock or a mixture of rock and dirt has continued to present challenges to those in the industry.
Various attempts have been made to achieve this directional control. These attempts have either proved largely unsuccessful due to the rough and demanding downhole environment to which the drilling apparatus is subjected, or involved an elaborate and expensive mechanism in an effort to change the drilling orientation angle. For example, the Schoeffler U.S. Pat. No. 4,732,223, and the Warren U.S. Pat. No. 5,547,031, and the Eddison U.S. Pat. No. 5,520,256, each describe an elaborate mechanical system to alter the angle of orientation of the drill head. In the '223 patent, a clutch mechanism is employed to lock the exterior housing and to activate a hydraulic deflection mechanism utilizing the drilling fluid so as to elastically deflect the drilling shaft which pivotally alters the angular orientation of the drill head. The '256 patent employs a mud motor and a drill bit coupling mechanism comprised of multiple housings, the lower of which has an upper and drill bit coupling joined together to define a bend angle allowing for the line of drilling to turn, which radius of curvature is enhanced by the extension of a hydraulic piston which results in a shift of opposed pads against the low side of the borehole increasing the bend angle and sharpening the radius of curvature. The '031 patent employs an internal flexible joint comprised of a ball-shaped member seated in a spherical housing combined with a hydraulically actuated blade on the exterior of the housing which can be extended outwardly against the surface of the borehole to cam the housing to one side of the borehole thereby changing the angle of orientation for the drill head due to the resultant movement within the flexible joint.
The Kinnan U.S. Pat. No. 5,449,046, discusses a detailed steerable drilling apparatus for lateral underground drilling. This is the primary area of use anticipated with the present invention. The '046 patent employs a series of hydraulically driven pistons which are actuated outwardly against the side of the borehole to deflect the drill head housing in an opposing direction thereby altering the angle of the drilling.
Another example of an elaborate internal mechanism utilized to steer the drilling head is found in the Eddison U.S. Pat. No. 5,529,133. Similar to the '256 and '031 patent, this apparatus utilizes a circumferential coupling system that allows the drill head to be affixed at an angle differing from the axis of the drilling shaft.
The Brotherton U.S. Pat. No. 5,490,569 is similar to the '223 patent in that it incorporates a flexible shaft mounted within the housing in such a manner that when the shaft is elastically deflected, it alters the angle of orientation of the drill head in relation to the axis of the drill housing. It utilizes an outer sleeve to prevent the housing from turning down hole when the shaft is actuated turning the bit. This external sleeve extends the entire length of the drill string and is also utilized to change the orientation of the housing thereby changing the angle of orientation of the drill head so as to drill in a differing direction.
A final problem not adequately addressed by the various apparatus involves the functionality of the steering mechanism and the speed of the progress when drilling through less than ideal soil conditions. The currently available devices proceed through rocky conditions at a labored rate resulting in additional expenses to the contractor.